Downsizing and boosting is a way to meet increased demand for more efficient vehicles. Turbocharged and supercharged engines may be configured to compress ambient air entering the engine in order to increase power. Compression of the air may cause an increase in air temperature, thus, a charge air cooler (CAC) may be utilized to cool the heated air thereby increasing its density and further increasing the potential power of the engine. Condensate may form in the CAC when the ambient air temperature decreases, or during humid or rainy weather conditions, where the intake air is cooled below the water dew point. The addition of a low pressure (LP) EGR loop additionally increases the water vapor content in the CAC and thus makes condensation more likely. Due to CAC geometry and lower air velocities, a substantial amount of water is not carried with the air and is retained in the CAC. Condensate may collect at the bottom of the CAC, or in the internal passages, and cooling turbulators. Water retained in the CAC may cause problems such as freezing damage and a reduction in CAC effectiveness. Additionally, under certain air flow conditions, condensate may exit the CAC and enter an intake manifold of the engine as water droplets. If too much condensate is ingested by the engine, engine misfire and/or combustion instability may occur.
One approach to address condensate formation in the CAC is shown by Palm in U.S. Patent No. 20110094219 A1. Therein, condensate discharged from the cooler is collected in a condensation trap coupled to an outside surface of a bend in an outlet duct of the cooler such that condensate may be stored and later released to the intake manifold. However, the inventors herein have recognized potential issues with such a system. As one example, while stored condensate may be released at such a rate that the amount of water leaving the condensation trap does not interfere with engine operation, precise control over the amount of water released to the engine under specific engine operating conditions is not achieved.
Thus, the inventors herein have developed methods to at least partially address the above issues. In one example, a method is provided comprising collecting condensate from cooling air routed into an engine, routing said condensate into the engine via one of a plurality of locations based on operating conditions of said engine, determining a desired percentage of dilution for combustion in said engine based on said operating conditions, and adjusting said condensate injection and adjusting recirculation of exhaust gases from said engine to form said desired dilution based in part on said injection location. In this way, condensation collected from the CAC may comprise a renewable onboard water source that may be advantageously utilized to meet engine dilution requirements, and in addition, reduced CAC effectiveness and potential CAC damage as a result of condensation collection and/or freezing may be addressed by removing condensation from the CAC and storing said condensate in a reservoir.
In one example, determining a desired percentage of dilution for combustion in said engine is based on said operating conditions to keep NOx in combustion gases below desired amounts and to avoid ignition knock in said engine. In this way, engine performance and efficiency may be addressed, and harmful emissions may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.